This invention pertains to a scanner profiling system for locating and "mapping" a selected feature in a three-dimensional object, which feature is nearest with respect to a defined datum plane. More specifically, the invention pertains to such a system wherein scanning-derived data are used in conjunction with a digital computer to focus the scanning attention of the system particularly toward the selected feature. For the purpose of illustration herein, the system of the invention is described with particular reference to handling two different profiling problems commonly encountered in a saw mill.
In recent years, there has been an ever increasing amount of concern paid to minimizing the amount of wood waste generated in a saw mill. There are many reasons for this growing concern. To begin with, timber resources, and particularly resources of large-diameter timber, having dwindled significantly. Saw mill operators, faced with this situation, have recognized the need to maximize yield from the smaller-available logs, with particular attention paid to accurate placement of saw cuts so as to minimize processing wastes.
A further trend in the saw-mill industry has been the increasing use of computers to monitor and control various mill operations. For example, it has been conventional for many years to have saw-cut decisions made by an experienced mill person who "reads" a log, cant, board, etc. and then personally decides where to place the workpiece (which is to be cut) relative to a saw blade to obtain maximum yield. The modern trend of harnessing computers to such a task has seen widespread incorporation in saw mills of so-called optical scanners which take over, with a significantly higher degree of accuracy, the task of "reading" the object to be cut. Data derived from these scanners is fed, typically, into a digital computer, which then performs one or more calculations to determine where a cut or cuts in the object should be made. The computer, further, and on the basis of such determination, outputs appropriate control signals to effect automatic manipulation and cutting of the object.
Two typical decision-making tasks which are presented in a saw mill, and with respect to which an embodiment of the present invention is described below, include the decision of how to position an uncut log for what is known as the opening-face cut in a head-rig band saw, and the determination, with respect to cants which are cut from a log, of how to place such cants with respect to edger saws to remove what is known as the wane portions in the cants.
In the case of deciding how to position an uncut log for an opening-face cut, an important feature in the log is what might be thought of as the ridge-like path of the portion of the log which is nearest to the cutting plane of the head-rig saw blade. By scanning a log preparatory to its being fed into a head-rig apparatus, and thereby locating this "near point" ridge, data are obtainable to enable proper positioning of the log relative to the saw blade.
A feature which is important in determining how to trim the edges of a cant to get rid of wane is the line of joinder between the wane and the adjacent sawn face of the cant. By mapping or locating this line of joinder, data, again, are readily obtainable to position the cant appropriately relative to an edger saw blade.
A general object of the present invention is to provide a unique scanner profiling system which is capable of performing profiling tasks, like those just briefly outlined above, with an extremely high degree of accuracy and efficiency.
More particularly, an object of the invention is to provide such a system wherein scanning apparatus is designed with a relatively wide-range scanning field (to accommodate object features which may be distributed, for various objects, at different widely spaced locations in the field), and which further includes control equipment that monitors incoming scan data with respect to an object, so as to direct scanning "attention" particularly only to that portion of the total scanning field where the particular object feature that is being mapped is located.
Expressed in somewhat greater detail, the scanning system of the invention operates in what is referred to herein as an adaptive scanning mode, wherein successive scanning sweeps throughout a scanning operation are progressively centered on the last-noted axial position of the feature towards which the scanning system's attention is directed. For example, with the system of the present invention, and considering its use in scanning the side of a log being prepared for feeding to a head-rig apparatus, range data derived from each successive scanning sweep (which moves substantially transverse to the log's longitudinal axis) are monitored to detect the point on the log noted in the sweep which is nearest to the plane of the head-rig saw blade, and the position of this point relative to the long axis of the scanning sweep. With such notation, the next successive scanning sweep is located so that its central point (i.e. between its opposite ends) is centered on the longitudinal location (relative to the scan sweep's axis) of the last-noted near point. Thus, with a bent or crooked log, successive adjacent scanning sweeps that are distributed along the length of the log are adjusted longitudinally relative to one another to maintain the scanning system's attention substantially centered on the near-point ridge feature in the log. As a consequence of such an adaptive scanning operation, accurate mapping information is obtained in a minimal amount of time.
Various other features and advantages which are offered by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.